I have the following simple MySQL query:
SELECT SQL_NO_CACHE mainID
FROM tableName
WHERE otherID3=19
AND dateStartCol >= '2012-08-01'
AND dateStartCol <= '2012-08-31';
When I run this it takes 0.29 seconds to bring back 36074 results. When I increase my date period to bring back more results (65703) it runs in 0.56. When I run other similar SQL queries on the same server but on different tables (some tables are larger) the results come back in approximately 0.01 seconds.
Although 0.29 isn’t slow – this is a basic part for a complex query and this timing means that it is not scalable.
See below for the table definition and indexes.
I know it’s not server load as I have the same issue on a development server which has very little usage.
+---------------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------------------+--------------+------+-----+---------+----------------+
| mainID | int(11) | NO | PRI | NULL | auto_increment |
| otherID1 | int(11) | NO | MUL | NULL | |
| otherID2 | int(11) | NO | MUL | NULL | |
| otherID3 | int(11) | NO | MUL | NULL | |
| keyword | varchar(200) | NO | MUL | NULL | |
| dateStartCol | date | NO | MUL | NULL | |
| timeStartCol | time | NO | MUL | NULL | |
| dateEndCol | date | NO | MUL | NULL | |
| timeEndCol | time | NO | MUL | NULL | |
| statusCode | int(1) | NO | MUL | NULL | |
| uRL | text | NO | | NULL | |
| hostname | varchar(200) | YES | MUL | NULL | |
| IPAddress | varchar(25) | YES | | NULL | |
| cookieVal | varchar(100) | NO | | NULL | |
| keywordVal | varchar(60) | NO | | NULL | |
| dateTimeCol | datetime | NO | MUL | NULL | |
+---------------------------+--------------+------+-----+---------+----------------+
+--------------------+------------+-------------------------------+--------------+---------------------------+-----------+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+--------------------+------------+-------------------------------+--------------+---------------------------+-----------+-------------+----------+--------+------+------------+---------+
| tableName | 0 | PRIMARY | 1 | mainID | A | 661990 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_otherID1 | 1 | otherID1 | A | 330995 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_otherID2 | 1 | otherID2 | A | 25 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_otherID3 | 1 | otherID3 | A | 48 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_dateStartCol | 1 | dateStartCol | A | 187 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_timeStartCol | 1 | timeStartCol | A | 73554 | NULL | NULL | | BTREE | |
|tableName | 1 | idx_dateEndCol | 1 | dateEndCol | A | 188 | NULL | NULL | | BTREE | |
|tableName | 1 | idx_timeEndCol | 1 | timeEndCol | A | 73554 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_keyword | 1 | keyword | A | 82748 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_hostname | 1 | hostname | A | 2955 | NULL | NULL | YES | BTREE | |
| tableName | 1 | idx_dateTimeCol | 1 | dateTimeCol | A | 220663 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_statusCode | 1 | statusCode | A | 2 | NULL | NULL | | BTREE | |
+--------------------+------------+-------------------------------+--------------+---------------------------+-----------+-------------+----------+--------+------+------------+---------+
Explain Output:
+----+-------------+-----------+-------+----------------------------------+-------------------+---------+------+-------+----------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
+----+-------------+-----------+-------+----------------------------------+-------------------+---------+------+-------+----------+-------------+
| 1 | SIMPLE | tableName | range | idx_otherID3,idx_dateStartCol | idx_dateStartCol | 3 | NULL | 66875 | 75.00 | Using where |
+----+-------------+-----------+-------+----------------------------------+-------------------+---------+------+-------+----------+-------------+
If that is really your query (and not a simplified version of same), then this ought to achieve best results:
The first index entry means that the first match in the
WHEREis very fast; the same also applies withdateStartCol. The third field is very small and does not slow the index appreciably, but allows for the datum you require to be found immediately in the index with no table access at all.It is important that the keys are in the same index. In the
EXPLAINyou posted, each key is in an index of its own, so even if MySQL chooses the best index, the performances will not be optimal. I’d try and use less indexes, for they also have a cost (shameless plug: Can Indices actually decrease SELECT performance? ).